MELBOURNE/MOSCOW (Reuters) – Russian aluminum giant Rusal on Friday warned of expected harm to its business from U.S. sanctions, sending its shares down more than 7 percent despite the company reporting a 20 percent jump in first-quarter core profit.

Washington last month announced sanctions on Russian billionaire Oleg Deripaska and several companies in which he is a large shareholder, including Rusal, En+ Group and GAZ Group, in response to what the United States said were Russia’s “malign activities”.

Though Rusal, the world’s biggest aluminum producer, said longer-term effects of the sanctions and the threat of additional future sanctions are difficult to determine, the company said it warned that the impact is highly likely to be “materially adverse”.

“In present circumstances, any forecast or outlook made or previously made should be deemed unreliable and may become irrelevant due to ongoing developments on the market at this period of time,” it said.

Rusal’s Hong Kong-listed shares were down 7.4 percent by 0759 GMT, reducing its market capitalization to $4.2 billion, according to the ThomsonReuters data. The company has lost about 60 percent of its value since the sanctions were announced on April 6.